Implementation of RC4 Encryption and URL encoding in objective c - ios

Question

I've to implement the RC4 encryption algorithm in my application for URL encoding.The sample part is listed below for your reference.
Actual value Before Encryption : 10/28/2013
Expected value After Encryption : ˆ!˜·hÇÔÞò
After URL encoding it should be : %0C%88%21%98%B7h%C7%D4%DE%F2
KEY USED is:#"psw"
I've tried but value after encryption & URL encoding returns in this way:
After encryption : !·hÇÔÞò
After URL encoding : %0C%C2%88%21%C2%98%C2%B7h%C3%87%C3%94%C3%9E%C3%B2
I tried converting the java code into objective c code.The java code works fine ,were as the objective c is not working, which you can see in the above result.
Here is the Java code
import java.net.URLEncoder;
public class RC4 {
private char[] key;
private int[] sbox;
private static final int SBOX_LENGTH = 256;
private static final int KEY_MIN_LENGTH = 1;
public static void main(String[] args) {
try {
RC4 rc4 = new RC4("psw");
char[] result = rc4.encrypt("10/28/2013".toCharArray());
System.out.println("encrypted string:\n"
+ new String(toByteArray(result)));
System.out.println("decrypted string:\n"
+ new String(rc4.decrypt(result)));
System.out.println("decrypted string:\n"
+ URLEncoder.encode(new String(toByteArray(result))));
} catch (InvalidKeyException e) {
System.err.println(e.getMessage());
}
}
static byte[] toByteArray(char[] chars) {
byte[] bytes = new byte[chars.length];
for (int i = 0; i < chars.length; i++) {
// bytes[i*2] = (byte) (chars[i] >> 8);
bytes[i] = (byte) chars[i];
}
return bytes;
}
public RC4(String key) throws InvalidKeyException {
setKey(key);
}
public RC4() {
}
public char[] decrypt(final char[] msg) {
return encrypt(msg);
}
public char[] encrypt(final char[] msg) {
sbox = initSBox(key);
char[] code = new char[msg.length];
int i = 0;
int j = 0;
for (int n = 0; n < msg.length; n++) {
i = (i + 1) % SBOX_LENGTH;
j = (j + sbox[i]) % SBOX_LENGTH;
swap(i, j, sbox);
int rand = sbox[(sbox[i] + sbox[j]) % SBOX_LENGTH];
code[n] = (char) (rand ^ (int) msg[n]);
}
return code;
}
private int[] initSBox(char[] key) {
int[] sbox = new int[SBOX_LENGTH];
int j = 0;
for (int i = 0; i < SBOX_LENGTH; i++) {
sbox[i] = i;
}
for (int i = 0; i < SBOX_LENGTH; i++) {
j = (j + sbox[i] + key[i % key.length]) % SBOX_LENGTH;
swap(i, j, sbox);
}
return sbox;
}
private void swap(int i, int j, int[] sbox) {
int temp = sbox[i];
sbox[i] = sbox[j];
sbox[j] = temp;
}
public void setKey(String key) throws InvalidKeyException {
if (!(key.length() >= KEY_MIN_LENGTH && key.length() < SBOX_LENGTH)) {
throw new InvalidKeyException("Key length has to be between "
+ KEY_MIN_LENGTH + " and " + (SBOX_LENGTH - 1));
}
this.key = key.toCharArray();
}
public class InvalidKeyException extends Exception {
private static final long serialVersionUID = 1L;
public InvalidKeyException(String message) {
super(message);
}
}
}
Its corresponding Objective c Code
-(NSString *)encrypt:(NSString *)string{
[self frameSBox:#"psw"];
unichar code[string.length];
const unichar* buffer = code;
int i = 0;
int j = 0;
for (int n = 0; n < string.length; n++) {
i = (i + 1) % self.SBOX_LENGTH;
j = (j + [[self.sBox objectAtIndex:i]integerValue]) % self.SBOX_LENGTH;
[self swap:i with:j];
int index=([[self.sBox objectAtIndex:i] integerValue]+[[self.sBox objectAtIndex:j] integerValue]);
int rand=([[self.sBox objectAtIndex:(index%self.SBOX_LENGTH)] integerValue]);
code[n]=(rand ^ (int)[string characterAtIndex:n]);
}
buffer = code;
return [NSString stringWithCharacters:buffer length:string.length];
}
-(NSArray *)frameSBox:(NSString *)keyValue{
if (self.sBox == nil) {
self.sBox=[[NSMutableArray alloc]init];
}
self.SBOX_LENGTH=256;
int j = 0;
for (int i = 0; i < self.SBOX_LENGTH; i++) {
[self.sBox addObject:[NSNumber numberWithInteger:i]];
}
for (int i = 0; i < self.SBOX_LENGTH; i++) {
j = (j + [[self.sBox objectAtIndex:i] integerValue] + [keyValue characterAtIndex:(i % keyValue.length)]) % self.SBOX_LENGTH;
[self swap:i with:j];
}
return self.sBox;
}
-(void)swap:(int)i with:(int)j{
id tempObj = [self.sBox objectAtIndex:i];
[self.sBox replaceObjectAtIndex:i withObject:[self.sBox objectAtIndex:j]];
[self.sBox replaceObjectAtIndex:j withObject:tempObj];
}
//I'm calling in a different class by creating the RC4encryptor object
NSString *unescaped = [[RC4StringEncryptor encryptor] encrypt:#"10/28/2013"];
logDebug(#"the value is:%#",unescaped);
NSString *escapedString = (NSString *)CFBridgingRelease(CFURLCreateStringByAddingPercentEscapes(
NULL,
(__bridge CFStringRef) unescaped,
NULL,
CFSTR("!*'();:#&=+$,/?%#[]\" "),
kCFStringEncodingUTF8));
NSLog(#"escapedString: %#",escapedString);
I've also tried
#import <CommonCrypto/CommonCryptor.h>
#implementation NSData (RC4)
- (NSData *)RC4EncryptWithKey:(NSString *)key {
char keyPtr[kCCKeySizeMinRC4+1];
bzero(keyPtr, sizeof(keyPtr));
[key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];
NSUInteger dataLength = [self length];
size_t bufferSize = dataLength + kCCKeySizeMinRC4;
void *buffer = malloc(bufferSize);
size_t numBytesEncrypted = 0;
CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmRC4, kCCModeRC4,
keyPtr, kCCKeySizeMinRC4,
NULL ,
[self bytes], dataLength,
buffer, bufferSize,
&numBytesEncrypted);
if (cryptStatus == kCCSuccess) {
return [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted];
}
free(buffer);
return nil;
}
- (NSData*) encryptString:(NSString*)plaintext withKey:(NSString*)key {
return [[plaintext dataUsingEncoding:NSUTF8StringEncoding] RC4EncryptWithKey:key];
}
But this above code doesn't work for me.Kindly help me in this....

Answer 1

Somehow I fixed your code and it encrypts-decrypts perfectly. Here it is:
#interface RC4Crypt()
#property (nonatomic, strong) NSArray * key;
#property (nonatomic, strong) NSMutableArray * sBox;
#end
#implementation RC4Crypt
static const int SBOX_LENGTH = 256;
static const int KEY_MIN_LENGTH = 1;
-(NSString *)encrypt:(NSString *)string withKey:(NSString *)key{
self.sBox = [[self frameSBox:key] mutableCopy];
unichar code[string.length];
int i = 0;
int j = 0;
for (int n = 0; n < string.length; n++) {
i = (i + 1) % SBOX_LENGTH;
j = (j + [[self.sBox objectAtIndex:i]integerValue]) % SBOX_LENGTH;
[self.sBox exchangeObjectAtIndex:i withObjectAtIndex:j];
int index=([self.sBox[i] integerValue]+[self.sBox[j] integerValue]);
int rand=([self.sBox[(index%SBOX_LENGTH)] integerValue]);
code[n]=(rand ^ (int)[string characterAtIndex:n]);
}
const unichar* buffer;
buffer = code;
return [NSString stringWithCharacters:buffer length:string.length];
}
- (NSString*) decrypt:(NSString*)string withKey:(NSString*)key
{
return [self encrypt:string withKey:key];
}
-(NSArray *)frameSBox:(NSString *)keyValue{
NSMutableArray *sBox = [[NSMutableArray alloc] initWithCapacity:SBOX_LENGTH];
int j = 0;
for (int i = 0; i < SBOX_LENGTH; i++) {
[sBox addObject:[NSNumber numberWithInteger:i]];
}
for (int i = 0; i < SBOX_LENGTH; i++) {
j = (j + [sBox[i] integerValue] + [keyValue characterAtIndex:(i % keyValue.length)]) % SBOX_LENGTH;
[sBox exchangeObjectAtIndex:i withObjectAtIndex:j];
}
return [NSArray arrayWithArray:sBox];
}
#end